Reacting To!

This can be considered an Au since Papyrus and Sans have little to nothing on their past so I will be adding some stuff I don't thinks it's possible to make a canon past undertale since you don't know how old characters are compared to some and if they ever met each other before...
Asgore, Toriel, Asriel, Chara, Gaster, Sans, Papyrus, Undyne, and Alphys will be reacting